Japanese Patent Laid-Open No. 2006-88880 describes an air current separation reducing sheet to be applied to the exterior of an automobile provided with a plurality of recesses formed in the surface.
Japanese Patent Laid-Open Nos. 2003-226134 and 2008-273224 individually describe an automobile in which discharge needles connected to a high-voltage generator are arranged in an air duct guiding air from an air conditioner to a vehicle interior and a door trim so that ionized air resulting from corona discharge from a leading end of the discharge needle is supplied to the vehicle interior.
However, the silicon rubber sheet having an uneven surface taught by JP-A-2006-88880 may cause disfigurement of a vehicle if attached to a vehicle surface. In addition, the silicon rubber sheet may be electrostatically charged easily during propulsion of the vehicle. Consequently, air may be separated from the sheet attached to the vehicle surface by repulsive force acting between the ionized air and static electricity on the sheet.
As described, Japanese Patent Laid-Open Nos. 2003-226134 and 2008-273224 individually describe an automobile in which ionized air is supplied to the vehicle interior. However, those prior art documents do not focus on a relation between the static electricity accumulating on the vehicle surface and aerodynamic characteristics of airflow flowing along the vehicle surface. Basically, air is charged positively and hence repulsive force acts between the airflow and the vehicle surface. Consequently, air may be separated from the vehicle surface by such repulsive force.
If the airflow is separated from the vehicle surface, desired aerodynamic characteristics of the vehicle may not be achieved and consequently driving performance of the vehicle may be degraded.